The present invention relates generally to polymer gel compositions and, more particularly, to swellable polymer gel compositions. The invention further relates to methods of using swellable polymer gel compositions in subterranean formations.
The present invention is directed to a swellable polymer gel composition for use with an aqueous solution. The composition comprises water, a water soluble polymer, a water soluble crosslinking system and a swelling agent. The amounts of the polymer and the crosslinking system are effective to form a substantially uniformly reacted gel structure. The amount of the swelling agent is calculated to maintain or increase the volume of the gel a predetermined percentage when the swelling agent contacts the aqueous solution.
The present invention is further directed to a swellable polymer gel composition for use with an aqueous solution. The composition comprises water, a water soluble polymer, a water soluble crosslinking system, a strengthening agent and a swelling agent.
The water comprises from about 75 percent to about 99 percent of the weight of the composition. The water soluble polymer comprises a mixture of polymers. The mixture of polymers comprises carboxymethylcellulose having from about a 0.65 degree of substitution to about a 0.95 degree of substitution and partially hydrolyzed polyacrylamide with a degree of hydrolysis ranging from about 10 to about 20 percent. The weight of each polymer in the mixture of polymers is from about 0.01 to about 0.35 percent of the weight of the composition and the polymers in the mixture of polymers are combined in about a 50/50 ratio.
The water soluble crosslinking system comprises a water soluble crosslinking agent and a water soluble reducing agent. The crosslinking agent is sodium dichromate, and the weight of the sodium dichromate is from about 0.2 to about 60 percent of the weight of the polymer. The reducing agent is sodium thiosulfate or ammonium thiosulfate, and the weight of the reducing agent is from about 150 to about 500 percent of the weight of the sodium dichromate.
The strengthening agent comprises a mixture of diatomaceous earth and barite. The weight of the strengthening agent is from about 0.01 to about 25 percent of the weight of the composition.
The swelling agent is selected from the group consisting of crosslinked sodium salt of polyacrylate, crosslinked acrylamide potassium copolymer, and crosslinked acrylamide sodium copolymer. The weight of the swelling agent is from about 0.3 to about 5 percent of the weight of the composition.
The present invention is further directed to a swellable polymer gel composition for use with an aqueous solution, the swellable polymer gel comprising water, a water soluble polymer, a water soluble crosslinking system, a strengthening agent and a swelling agent.
The water comprises from about 75 percent to about 87 percent of the weight of the composition. The water soluble polymer comprises a mixture of polymers. The mixture comprises carboxymethylcellulose having from about a 0.65 degree of substitution to about a 0.95 degree of substitution and partially hydrolyzed polyacrylamide having a degree of hydrolysis ranging from about a 10 to about a 20 percent. The weight of each polymer in the mixture of polymers is from about 0.01 to about 0.35 percent of the weight of the composition, and the polymers in the mixture of polymers are combined in about a 50/50 ratio.
The water soluble crosslinking system comprises a water soluble crosslinking agent and a chelating agent. The crosslinking agent is zirconium lactate comprising from about 0.75 to about 3 percent of the weight of the composition.
The strengthening agent comprises a mixture of diatomaceous earth and barite. The weight of the strengthening agent is from about 0.01 to about 25 percent of the weight of the composition.
The swelling agent is selected from the group consisting of crosslinked sodium salt of polyacrylate, crosslinked acrylamide potassium copolymer, and crosslinked acrylamide sodium copolymer. The weight of the swelling agent is from about 0.3 to about 5 percent of the weight of the composition.
The present invention is further directed to a swellable polymer gel composition for use with an aqueous solution. The composition comprises water, a water soluble polymer, a water soluble crosslinking system, a strengthening agent and a swelling agent.
The water comprises from about 75 percent to about 99 percent of the weight of the composition. The water soluble polymer comprises a mixture of polymers. The mixture of polymers comprises carboxymethylcellulose having from about a 0.65 degree of substitution to about a 0.95 degree of substitution and partially hydrolyzed polyacrylamide with a degree of hydrolysis ranging from about 10 to about 20 percent. The weight of each polymer in the mixture of polymers is from about 0.08 to about 1 percent of the weight of the composition and the polymers in the mixture of polymers are combined in a ratio of about 70 percent carboxymethylcellulose to about 30 percent partially hydrolyzed polyacrylamide.
The water soluble crosslinking system comprises a water soluble crosslinking agent and a water soluble reducing agent. The crosslinking agent is sodium dichromate, and the weight of the sodium dichromate is from about 0.2 to about 60 percent of the weight of the polymer. The reducing agent is sodium thiosulfate or ammonium thiosulfate, and the weight of the reducing agent is from about 150 to about 500 percent of the weight of the sodium dichromate.
The strengthening agent comprises a mixture of diatomaceous earth and barite. The weight of the strengthening agent is from about 0.01 to about 25 percent of the weight of the composition.
The swelling agent is selected from the group consisting of crosslinked sodium salt of polyacrylate, crosslinked acrylamide potassium copolymer, and crosslinked acrylamide sodium copolymer. The weight of the swelling agent is from about 0.3 to about 5 percent of the weight of the composition.
The present invention is further directed to a swellable polymer gel composition for use with an aqueous solution, the swellable polymer gel comprising water, a water soluble polymer, a water soluble crosslinking system, a strengthening agent and a swelling agent.
The water comprises from about 75 percent to about 87 percent of the weight of the composition. The water soluble polymer comprises a mixture of polymers. The mixture comprises carboxymethylcellulose having from about a 0.65 degree of substitution to about a 0.95 degree of substitution and partially hydrolyzed polyacrylamide having from about a 10 to about a 20 percent degree of hydrolysis. The weight of each polymer in the mixture of polymers is from about from about 0.08 to about 1 percent of the weight of the composition, and the polymers in the mixture of polymers are combined in a ratio of about 70 percent carboxymethylcellulose to about 30 percent partially hydrolyzed polyacrylamide.
The water soluble crosslinking system comprises a water soluble crosslinking agent and a chelating agent. The crosslinking agent is zirconium lactate comprising from about 0.75 to about 3 percent of the weight of the composition.
The strengthening agent comprises a mixture of diatomaceous earth and barite. The weight of the strengthening agent is from about 0.01 to about 25 percent of the weight of the composition.
The swelling agent is selected from the group consisting of crosslinked sodium salt of polyacrylate, crosslinked acrylamide potassium copolymer, and crosslinked acrylamide sodium copolymer. The weight of the swelling agent is from about 0.3 to about 5 percent of the weight of the composition.
Still further, the present invention is directed to a method for treating a subterranean formation. The method comprises the step of introducing a swellable composition into the formation in the area requiring treatment. The swellable composition comprises a water soluble polymer, a water soluble crosslinking system, and a swelling agent. The amounts of the polymer and the crosslinking system are effective to form a substantially uniformly reacted gel structure. The amount of the swelling agent is calculated to increase the volume of the gel a predetermined percentage when the swelling agent contacts the aqueous solution.
The present invention is further directed to a method for removably plugging an oil and gas well which is to be abandoned. The method comprises the step of plugging the wellbore with a composition, wherein the composition is removable from the wellbore by circulating a fluid through the wellbore.
Finally, the present invention is directed to a method for restoring to service an abandoned oil and gas well plugged with a composition removable from the wellbore. The method comprises the step of removing the composition from the wellbore by circulating a fluid through the wellbore.